Some compounds exist as crystals with specific amounts of water molecules built in. For example, barium hydroxide exists in two forms:
Ba(OH)2 anhydrous barium hydroxide Ba(OH)2·8H2O barium hydroxide octahydrate
When the water is present in the crystal, the compound is said to be hydrated, and the number of waters is included in the name as shown above. For this section you will measure the mass % of water in copper (II) sulfate pentahydrate by heating it to an anhydrous compound.
1. Obtain about 3.0 grams of copper (II) sulfate pentahydrate in an evaporating dish. Make sure you record all the data necessary to calculate the mass as precisely as our balances allow.
2. Record the appearance of copper sulfate pentahydrate:
3. Heat the compound over a medium Bunsen burner flame. Let the compound cool, stir it around with a glass stirring rod, and heat it again.
4. When the compound has cooled for a second time, record the necessary data to determine the mass of the anhydrous copper (II) sulfate remaining.
5. Determine the mass of water driven off by the Bunsen burner, and the mass percent of water in the original compound.
6. Write the skeleton equation for the reaction in which copper (II) sulfate pentahydrate becomes anhydrous copper sulfate and water vapor.
7. Write the balanced equation for the reaction in which copper (II) sulfate pentahydrate becomes anhydrous copper (II) sulfate and water vapor.
8. What type of reaction was this? Circle one: (Synthesis, etc)
9. Show the complete proper data table and calculations for steps 1, 4, and 5 on the back of this sheet.
[MHS Chem page]